Radio sensitivity measurement plays an important role in evaluating a radio frequency (RF) radio receiver's ability to detect a weak signal in either a controlled or real application environment. Radio sensitivity and receive antenna gain together determine the total isotropic sensitivity (TIS), which determines the radio downlink performance.
Radio sensitivity is defined as a receiving power level at the input of the radio when the bit error ratio (BER) of the radio reaches its threshold level. For a Global System for Mobile Communications (GSM) system, a BER of 2.44 is the defined threshold BER level. BER measurement accuracy and measurement time can directly affect radio sensitivity measurement accuracy and time.
The relationship of BER and sensitivity is shown in the graph of FIG. 9. Since BER fluctuates significantly in real sensitivity measurements, an average value of BER is typically used for estimating the sensitivity of the receiver. Yet, due to large spurious noise in the real communication environment and/or the radio itself, and sudden changes in the test environment, the average BER may even change significantly.
One exemplary approach for estimating a channel bit error ratio in a receiver is set forth in U.S. Pat. No. 6,792,053 to Vainio et al. A pseudo bit error ratio of a channel is determined in a receiver comprising detecting means for detecting a data sequence of a received signal, decoding means for decoding a first encoding of the detected data signal, and re-encoding means for re-encoding with the first encoding the data sequence decoded from the first encoding. The receiver further comprises quality determining means for providing the detected data sequence with a value for quality, and estimating means for estimating the bit error ratio-provided that the quality of the detected data sequence fulfils a predetermined quality requirement by comparing the detected data sequence with the data sequence re-encoded with first encoding.
Despite the existence of such systems, further improvements in determining or estimating BER in communications systems, particularly wireless communications systems, may be desirable.